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    This is the documentation for the Scala standard library.

    This is the documentation for the Scala standard library.

    Package structure

    The scala package contains core types like Int, Float, Array or Option which are accessible in all Scala compilation units without explicit qualification or imports.

    Notable packages include:

    Other packages exist. See the complete list on the right.

    Additional parts of the standard library are shipped as separate libraries. These include:

    • scala.reflect - Scala's reflection API (scala-reflect.jar)
    • scala.xml - XML parsing, manipulation, and serialization (scala-xml.jar)
    • scala.collection.parallel - Parallel collections (scala-parallel-collections.jar)
    • scala.util.parsing - Parser combinators (scala-parser-combinators.jar)
    • scala.swing - A convenient wrapper around Java's GUI framework called Swing (scala-swing.jar)

    Automatic imports

    Identifiers in the scala package and the scala.Predef object are always in scope by default.

    Some of these identifiers are type aliases provided as shortcuts to commonly used classes. For example, List is an alias for scala.collection.immutable.List.

    Other aliases refer to classes provided by the underlying platform. For example, on the JVM, String is an alias for java.lang.String.

    Definition Classes
    root
  • package scala

    Core Scala types.

    Core Scala types. They are always available without an explicit import.

    Definition Classes
    root
  • package util
    Definition Classes
    scala
  • package matching
    Definition Classes
    util
  • Regex
  • UnanchoredRegex
t

scala.util.matching

UnanchoredRegex

trait UnanchoredRegex extends Regex

A Regex that finds the first match when used in a pattern match.

Source
Regex.scala
See also

Regex#unanchored

Linear Supertypes
Regex, java.io.Serializable, AnyRef, Any
Type Hierarchy
Ordering
  1. Alphabetic
  2. By Inheritance
Inherited
  1. UnanchoredRegex
  2. Regex
  3. Serializable
  4. AnyRef
  5. Any
Implicitly
  1. by any2stringadd
  2. by StringFormat
  3. by Ensuring
  4. by ArrowAssoc
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Visibility
  1. Public
  2. All

Value Members

  1. final def !=(arg0: Any): Boolean

    Test two objects for inequality.

    Test two objects for inequality.

    returns

    true if !(this == that), false otherwise.

    Definition Classes
    AnyRef → Any
  2. final def ##(): Int

    Equivalent to x.hashCode except for boxed numeric types and null.

    Equivalent to x.hashCode except for boxed numeric types and null. For numerics, it returns a hash value which is consistent with value equality: if two value type instances compare as true, then ## will produce the same hash value for each of them. For null returns a hashcode where null.hashCode throws a NullPointerException.

    returns

    a hash value consistent with ==

    Definition Classes
    AnyRef → Any
  3. def +(other: String): String
    Implicit
    This member is added by an implicit conversion from UnanchoredRegex toany2stringadd[UnanchoredRegex] performed by method any2stringadd in scala.Predef.
    Definition Classes
    any2stringadd
  4. def ->[B](y: B): (UnanchoredRegex, B)
    Implicit
    This member is added by an implicit conversion from UnanchoredRegex toArrowAssoc[UnanchoredRegex] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc
    Annotations
    @inline()
  5. final def ==(arg0: Any): Boolean

    The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).

    The expression x == that is equivalent to if (x eq null) that eq null else x.equals(that).

    returns

    true if the receiver object is equivalent to the argument; false otherwise.

    Definition Classes
    AnyRef → Any
  6. def anchored: Regex
    Definition Classes
    Regex
  7. final def asInstanceOf[T0]: T0

    Cast the receiver object to be of type T0.

    Cast the receiver object to be of type T0.

    Note that the success of a cast at runtime is modulo Scala's erasure semantics. Therefore the expression 1.asInstanceOf[String] will throw a ClassCastException at runtime, while the expression List(1).asInstanceOf[List[String]] will not. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the requested type.

    returns

    the receiver object.

    Definition Classes
    Any
    Exceptions thrown

    ClassCastException if the receiver object is not an instance of the erasure of type T0.

  8. def clone(): AnyRef

    Create a copy of the receiver object.

    Create a copy of the receiver object.

    The default implementation of the clone method is platform dependent.

    returns

    a copy of the receiver object.

    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.CloneNotSupportedException]) @native()
    Note

    not specified by SLS as a member of AnyRef

  9. def ensuring(cond: (UnanchoredRegex) => Boolean, msg: => Any): UnanchoredRegex
    Implicit
    This member is added by an implicit conversion from UnanchoredRegex toEnsuring[UnanchoredRegex] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  10. def ensuring(cond: (UnanchoredRegex) => Boolean): UnanchoredRegex
    Implicit
    This member is added by an implicit conversion from UnanchoredRegex toEnsuring[UnanchoredRegex] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  11. def ensuring(cond: Boolean, msg: => Any): UnanchoredRegex
    Implicit
    This member is added by an implicit conversion from UnanchoredRegex toEnsuring[UnanchoredRegex] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  12. def ensuring(cond: Boolean): UnanchoredRegex
    Implicit
    This member is added by an implicit conversion from UnanchoredRegex toEnsuring[UnanchoredRegex] performed by method Ensuring in scala.Predef.
    Definition Classes
    Ensuring
  13. final def eq(arg0: AnyRef): Boolean

    Tests whether the argument (that) is a reference to the receiver object (this).

    Tests whether the argument (that) is a reference to the receiver object (this).

    The eq method implements an equivalence relation on non-null instances of AnyRef, and has three additional properties:

    • It is consistent: for any non-null instances x and y of type AnyRef, multiple invocations of x.eq(y) consistently returns true or consistently returns false.
    • For any non-null instance x of type AnyRef, x.eq(null) and null.eq(x) returns false.
    • null.eq(null) returns true.

    When overriding the equals or hashCode methods, it is important to ensure that their behavior is consistent with reference equality. Therefore, if two objects are references to each other (o1 eq o2), they should be equal to each other (o1 == o2) and they should hash to the same value (o1.hashCode == o2.hashCode).

    returns

    true if the argument is a reference to the receiver object; false otherwise.

    Definition Classes
    AnyRef
  14. def equals(arg0: AnyRef): Boolean

    The equality method for reference types.

    The equality method for reference types. Default implementation delegates to eq.

    See also equals in scala.Any.

    returns

    true if the receiver object is equivalent to the argument; false otherwise.

    Definition Classes
    AnyRef → Any
  15. def finalize(): Unit

    Called by the garbage collector on the receiver object when there are no more references to the object.

    Called by the garbage collector on the receiver object when there are no more references to the object.

    The details of when and if the finalize method is invoked, as well as the interaction between finalize and non-local returns and exceptions, are all platform dependent.

    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.Throwable])
    Note

    not specified by SLS as a member of AnyRef

  16. def findAllIn(source: CharSequence): MatchIterator

    Return all non-overlapping matches of this Regex in the given character sequence as a scala.util.matching.Regex.MatchIterator, which is a special scala.collection.Iterator that returns the matched strings but can also be queried for more data about the last match, such as capturing groups and start position.

    Return all non-overlapping matches of this Regex in the given character sequence as a scala.util.matching.Regex.MatchIterator, which is a special scala.collection.Iterator that returns the matched strings but can also be queried for more data about the last match, such as capturing groups and start position.

    A MatchIterator can also be converted into an iterator that returns objects of type scala.util.matching.Regex.Match, such as is normally returned by findAllMatchIn.

    Where potential matches overlap, the first possible match is returned, followed by the next match that follows the input consumed by the first match:

    val hat  = "hat[^a]+".r
    val hathaway = "hathatthattthatttt"
    val hats = hat.findAllIn(hathaway).toList                     // List(hath, hattth)
    val pos  = hat.findAllMatchIn(hathaway).map(_.start).toList   // List(0, 7)

    To return overlapping matches, it is possible to formulate a regular expression with lookahead (?=) that does not consume the overlapping region.

    val madhatter = "(h)(?=(at[^a]+))".r
    val madhats   = madhatter.findAllMatchIn(hathaway).map {
      case madhatter(x,y) => s"$x$y"
    }.toList                                       // List(hath, hatth, hattth, hatttt)

    Attempting to retrieve match information after exhausting the iterator results in java.lang.IllegalStateException. See scala.util.matching.Regex.MatchIterator for details.

    source

    The text to match against.

    returns

    A scala.util.matching.Regex.MatchIterator of matched substrings.

    Definition Classes
    Regex
    Example:
    1. for (words <- """\w+""".r findAllIn "A simple example.") yield words
  17. def findAllMatchIn(source: CharSequence): Iterator[Match]

    Return all non-overlapping matches of this regexp in given character sequence as a scala.collection.Iterator of scala.util.matching.Regex.Match.

    Return all non-overlapping matches of this regexp in given character sequence as a scala.collection.Iterator of scala.util.matching.Regex.Match.

    source

    The text to match against.

    returns

    A scala.collection.Iterator of scala.util.matching.Regex.Match for all matches.

    Definition Classes
    Regex
    Example:
    1. for (words <- """\w+""".r findAllMatchIn "A simple example.") yield words.start
  18. def findFirstIn(source: CharSequence): Option[String]

    Return an optional first matching string of this Regex in the given character sequence, or None if there is no match.

    Return an optional first matching string of this Regex in the given character sequence, or None if there is no match.

    source

    The text to match against.

    returns

    An scala.Option of the first matching string in the text.

    Definition Classes
    Regex
    Example:
    1. """\w+""".r findFirstIn "A simple example." foreach println // prints "A"
  19. def findFirstMatchIn(source: CharSequence): Option[Match]

    Return an optional first match of this Regex in the given character sequence, or None if it does not exist.

    Return an optional first match of this Regex in the given character sequence, or None if it does not exist.

    If the match is successful, the scala.util.matching.Regex.Match can be queried for more data.

    source

    The text to match against.

    returns

    A scala.Option of scala.util.matching.Regex.Match of the first matching string in the text.

    Definition Classes
    Regex
    Example:
    1. ("""[a-z]""".r findFirstMatchIn "A simple example.") map (_.start) // returns Some(2), the index of the first match in the text
  20. def findPrefixMatchOf(source: CharSequence): Option[Match]

    Return an optional match of this Regex at the beginning of the given character sequence, or None if it matches no prefix of the character sequence.

    Return an optional match of this Regex at the beginning of the given character sequence, or None if it matches no prefix of the character sequence.

    Unlike findFirstMatchIn, this method will only return a match at the beginning of the input.

    source

    The text to match against.

    returns

    A scala.Option of the scala.util.matching.Regex.Match of the matched string.

    Definition Classes
    Regex
    Example:
    1. """\w+""".r findPrefixMatchOf "A simple example." map (_.after) // returns Some(" simple example.")
  21. def findPrefixOf(source: CharSequence): Option[String]

    Return an optional match of this Regex at the beginning of the given character sequence, or None if it matches no prefix of the character sequence.

    Return an optional match of this Regex at the beginning of the given character sequence, or None if it matches no prefix of the character sequence.

    Unlike findFirstIn, this method will only return a match at the beginning of the input.

    source

    The text to match against.

    returns

    A scala.Option of the matched prefix.

    Definition Classes
    Regex
    Example:
    1. """\p{Lower}""".r findPrefixOf "A simple example." // returns None, since the text does not begin with a lowercase letter
  22. def formatted(fmtstr: String): String

    Returns string formatted according to given format string.

    Returns string formatted according to given format string. Format strings are as for String.format (@see java.lang.String.format).

    Implicit
    This member is added by an implicit conversion from UnanchoredRegex toStringFormat[UnanchoredRegex] performed by method StringFormat in scala.Predef.
    Definition Classes
    StringFormat
    Annotations
    @inline()
  23. final def getClass(): Class[_ <: AnyRef]

    Returns the runtime class representation of the object.

    Returns the runtime class representation of the object.

    returns

    a class object corresponding to the runtime type of the receiver.

    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  24. def hashCode(): Int

    The hashCode method for reference types.

    The hashCode method for reference types. See hashCode in scala.Any.

    returns

    the hash code value for this object.

    Definition Classes
    AnyRef → Any
    Annotations
    @native()
  25. final def isInstanceOf[T0]: Boolean

    Test whether the dynamic type of the receiver object is T0.

    Test whether the dynamic type of the receiver object is T0.

    Note that the result of the test is modulo Scala's erasure semantics. Therefore the expression 1.isInstanceOf[String] will return false, while the expression List(1).isInstanceOf[List[String]] will return true. In the latter example, because the type argument is erased as part of compilation it is not possible to check whether the contents of the list are of the specified type.

    returns

    true if the receiver object is an instance of erasure of type T0; false otherwise.

    Definition Classes
    Any
  26. def matches(source: CharSequence): Boolean

    Returns whether this Regex matches the given character sequence.

    Returns whether this Regex matches the given character sequence.

    Like the extractor, this method takes anchoring into account.

    source

    The text to match against

    returns

    true if and only if source matches this Regex.

    Definition Classes
    Regex
    Example:
    1. """\d+""".r matches "123" // returns true
    See also

    Regex#unanchored

  27. final def ne(arg0: AnyRef): Boolean

    Equivalent to !(this eq that).

    Equivalent to !(this eq that).

    returns

    true if the argument is not a reference to the receiver object; false otherwise.

    Definition Classes
    AnyRef
  28. final def notify(): Unit

    Wakes up a single thread that is waiting on the receiver object's monitor.

    Wakes up a single thread that is waiting on the receiver object's monitor.

    Definition Classes
    AnyRef
    Annotations
    @native()
    Note

    not specified by SLS as a member of AnyRef

  29. final def notifyAll(): Unit

    Wakes up all threads that are waiting on the receiver object's monitor.

    Wakes up all threads that are waiting on the receiver object's monitor.

    Definition Classes
    AnyRef
    Annotations
    @native()
    Note

    not specified by SLS as a member of AnyRef

  30. val pattern: Pattern
    Definition Classes
    Regex
  31. def regex: String
    Definition Classes
    Regex
  32. def replaceAllIn(target: CharSequence, replacer: (Match) => String): String

    Replaces all matches using a replacer function.

    Replaces all matches using a replacer function. The replacer function takes a scala.util.matching.Regex.Match so that extra information can be obtained from the match. For example:

    import scala.util.matching.Regex
    val datePattern = new Regex("""(\d\d\d\d)-(\d\d)-(\d\d)""", "year", "month", "day")
    val text = "From 2011-07-15 to 2011-07-17"
    val repl = datePattern replaceAllIn (text, m => s"${m group "month"}/${m group "day"}")

    In the replacement String, a dollar sign ($) followed by a number will be interpreted as a reference to a group in the matched pattern, with numbers 1 through 9 corresponding to the first nine groups, and 0 standing for the whole match. Any other character is an error. The backslash (\) character will be interpreted as an escape character and can be used to escape the dollar sign. Use Regex.quoteReplacement to escape these characters.

    target

    The string to match.

    replacer

    The function which maps a match to another string.

    returns

    The target string after replacements.

    Definition Classes
    Regex
  33. def replaceAllIn(target: CharSequence, replacement: String): String

    Replaces all matches by a string.

    Replaces all matches by a string.

    In the replacement String, a dollar sign ($) followed by a number will be interpreted as a reference to a group in the matched pattern, with numbers 1 through 9 corresponding to the first nine groups, and 0 standing for the whole match. Any other character is an error. The backslash (\) character will be interpreted as an escape character and can be used to escape the dollar sign. Use Regex.quoteReplacement to escape these characters.

    target

    The string to match

    replacement

    The string that will replace each match

    returns

    The resulting string

    Definition Classes
    Regex
    Example:
    1. """\d+""".r replaceAllIn ("July 15", "<NUMBER>") // returns "July <NUMBER>"
  34. def replaceFirstIn(target: CharSequence, replacement: String): String

    Replaces the first match by a string.

    Replaces the first match by a string.

    In the replacement String, a dollar sign ($) followed by a number will be interpreted as a reference to a group in the matched pattern, with numbers 1 through 9 corresponding to the first nine groups, and 0 standing for the whole match. Any other character is an error. The backslash (\) character will be interpreted as an escape character and can be used to escape the dollar sign. Use Regex.quoteReplacement to escape these characters.

    target

    The string to match

    replacement

    The string that will replace the match

    returns

    The resulting string

    Definition Classes
    Regex
  35. def replaceSomeIn(target: CharSequence, replacer: (Match) => Option[String]): String

    Replaces some of the matches using a replacer function that returns an scala.Option.

    Replaces some of the matches using a replacer function that returns an scala.Option. The replacer function takes a scala.util.matching.Regex.Match so that extra information can be obtained from the match. For example:

    import scala.util.matching.Regex._
    
    val vars = Map("x" -> "a var", "y" -> """some $ and \ signs""")
    val text = "A text with variables %x, %y and %z."
    val varPattern = """%(\w+)""".r
    val mapper = (m: Match) => vars get (m group 1) map (quoteReplacement(_))
    val repl = varPattern replaceSomeIn (text, mapper)

    In the replacement String, a dollar sign ($) followed by a number will be interpreted as a reference to a group in the matched pattern, with numbers 1 through 9 corresponding to the first nine groups, and 0 standing for the whole match. Any other character is an error. The backslash (\) character will be interpreted as an escape character and can be used to escape the dollar sign. Use Regex.quoteReplacement to escape these characters.

    target

    The string to match.

    replacer

    The function which optionally maps a match to another string.

    returns

    The target string after replacements.

    Definition Classes
    Regex
  36. def runMatcher(m: Matcher): Boolean
    Attributes
    protected
    Definition Classes
    UnanchoredRegexRegex
  37. def split(toSplit: CharSequence): Array[String]

    Splits the provided character sequence around matches of this regexp.

    Splits the provided character sequence around matches of this regexp.

    toSplit

    The character sequence to split

    returns

    The array of strings computed by splitting the input around matches of this regexp

    Definition Classes
    Regex
  38. final def synchronized[T0](arg0: => T0): T0
    Definition Classes
    AnyRef
  39. def toString(): String

    The string defining the regular expression

    The string defining the regular expression

    returns

    a String representation of the object.

    Definition Classes
    Regex → AnyRef → Any
  40. def unanchored: UnanchoredRegex

    Create a new Regex with the same pattern, but no requirement that the entire String matches in extractor patterns and Regex#matches.

    Create a new Regex with the same pattern, but no requirement that the entire String matches in extractor patterns and Regex#matches.

    Normally, matching on date behaves as though the pattern were enclosed in anchors, "^pattern$".

    The unanchored Regex behaves as though those anchors were removed.

    Note that this method does not actually strip any matchers from the pattern.

    Calling anchored returns the original Regex.

    val date = """(\d\d\d\d)-(\d\d)-(\d\d)""".r.unanchored
    
    val date(year, month, day) = "Date 2011-07-15"                       // OK
    
    val copyright: String = "Date of this document: 2011-07-15" match {
      case date(year, month, day) => s"Copyright $year"                  // OK
      case _                      => "No copyright"
    }
    returns

    The new unanchored regex

    Definition Classes
    UnanchoredRegexRegex
  41. def unapplySeq(m: Match): Option[List[String]]

    Tries to match on a scala.util.matching.Regex.Match.

    Tries to match on a scala.util.matching.Regex.Match.

    A previously failed match results in None.

    If a successful match was made against the current pattern, then that result is used.

    Otherwise, this Regex is applied to the previously matched input, and the result of that match is used.

    Definition Classes
    Regex
  42. def unapplySeq(c: Char): Option[List[Char]]

    Tries to match the String representation of a scala.Char.

    Tries to match the String representation of a scala.Char.

    If the match succeeds, the result is the first matching group if any groups are defined, or an empty Sequence otherwise.

    For example:

    val cat = "cat"
    // the case must consume the group to match
    val r = """(\p{Lower})""".r
    cat(0) match { case r(x) => true }
    cat(0) match { case r(_) => true }
    cat(0) match { case r(_*) => true }
    cat(0) match { case r() => true }     // no match
    
    // there is no group to extract
    val r = """\p{Lower}""".r
    cat(0) match { case r(x) => true }    // no match
    cat(0) match { case r(_) => true }    // no match
    cat(0) match { case r(_*) => true }   // matches
    cat(0) match { case r() => true }     // matches
    
    // even if there are multiple groups, only one is returned
    val r = """((.))""".r
    cat(0) match { case r(_) => true }    // matches
    cat(0) match { case r(_,_) => true }  // no match
    c

    The Char to match

    returns

    The match

    Definition Classes
    Regex
  43. def unapplySeq(s: CharSequence): Option[List[String]]

    Tries to match a java.lang.CharSequence.

    Tries to match a java.lang.CharSequence.

    If the match succeeds, the result is a list of the matching groups (or a null element if a group did not match any input). If the pattern specifies no groups, then the result will be an empty list on a successful match.

    This method attempts to match the entire input by default; to find the next matching subsequence, use an unanchored Regex.

    For example:

    val p1 = "ab*c".r
    val p1Matches = "abbbc" match {
      case p1() => true               // no groups
      case _    => false
    }
    val p2 = "a(b*)c".r
    val p2Matches = "abbbc" match {
      case p2(_*) => true             // any groups
      case _      => false
    }
    val numberOfB = "abbbc" match {
      case p2(b) => Some(b.length)    // one group
      case _     => None
    }
    val p3 = "b*".r.unanchored
    val p3Matches = "abbbc" match {
      case p3() => true               // find the b's
      case _    => false
    }
    val p4 = "a(b*)(c+)".r
    val p4Matches = "abbbcc" match {
      case p4(_*) => true             // multiple groups
      case _      => false
    }
    val allGroups = "abbbcc" match {
      case p4(all @ _*) => all mkString "/" // "bbb/cc"
      case _            => ""
    }
    val cGroup = "abbbcc" match {
      case p4(_, c) => c
      case _        => ""
    }
    s

    The string to match

    returns

    The matches

    Definition Classes
    Regex
  44. final def wait(): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.InterruptedException])
  45. final def wait(arg0: Long, arg1: Int): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.InterruptedException])
  46. final def wait(arg0: Long): Unit
    Definition Classes
    AnyRef
    Annotations
    @throws(classOf[java.lang.InterruptedException]) @native()

Deprecated Value Members

  1. def [B](y: B): (UnanchoredRegex, B)
    Implicit
    This member is added by an implicit conversion from UnanchoredRegex toArrowAssoc[UnanchoredRegex] performed by method ArrowAssoc in scala.Predef.
    Definition Classes
    ArrowAssoc
    Annotations
    @deprecated
    Deprecated

    (Since version 2.13.0) Use -> instead. If you still wish to display it as one character, consider using a font with programming ligatures such as Fira Code.

Inherited from Regex

Inherited from java.io.Serializable

Inherited from AnyRef

Inherited from Any

Inherited by implicit conversion any2stringadd fromUnanchoredRegex to any2stringadd[UnanchoredRegex]

Inherited by implicit conversion StringFormat fromUnanchoredRegex to StringFormat[UnanchoredRegex]

Inherited by implicit conversion Ensuring fromUnanchoredRegex to Ensuring[UnanchoredRegex]

Inherited by implicit conversion ArrowAssoc fromUnanchoredRegex to ArrowAssoc[UnanchoredRegex]

Ungrouped